1. Field of the Invention
The present invention concerns a method and a device for transferring a number of data streams accumulating in parallel between units moving relative to one another, the digital data to be transferred being modulated so as to make the data at least somewhat resistant to generating interfering radiation, the data being transferred serially between the units and the data being demodulated after the transfer.
2. Description of the Prior Art
In the transfer of high data quantities, the problem of excessively high EMI (electromagnetic interference) radiation frequently occurs arise since the transferred data exhibit certain regularities that lead to the situation of high interference radiation arising in specific frequency ranges. Such interference radiation can negatively influence the operation of other apparatuses, or, possibly to the point of failure, such that it is necessary to keep this EMI radiation optimally low. Electromagnetic compatibility (EMC) standards exist for this purpose. This is in particular the case for medical apparatuses that are used in the environment of hospitals and clinics since here vital apparatuses could be disrupted in terms of their function.
At present this requirement inhibits the steadily growing quantity of data to be transferred in apparatuses such as, for example, computed tomography apparatuses, since this EMI problem becomes more severe as the data quantity increases.
WO 2004/032364 A1 and EP 1 051 816 B1 disclose approaches for reducing the EMI radiation in the data transfer between moving units can be achieved by an encoding of the data stream by encoding of transferred data therein.
European Patent EP 1 051 816 B1 describes a method for low-interference signal transfer of a digital signal from a transmitter to a spatially separated receiver, wherein a modulation unit modulates the entire signal to be transferred. It is necessary to design an additional transfer path between the transmitter and receiver with which a synchronization signal between the transmitter and the receiver can be transferred in order to be able to implement the demodulation of the modulated signals at the receiver in the correct manner.
A method for broadband transfer of digital signals in which the signals to be transferred are likewise encoded is known from WO 2004/032364 A1, wherein it is sought to adapt to the actual EMC situation by selecting different modulations that, for example, can be varied dependent on electrical measurement variables, in particular the currently measured interference level. The entire transferred signal is also encoded so that a separate transfer path for transfer of a synchronization signal for correct decoding of the transferred, encoded signals is necessary. Moreover, these methods have the disadvantage is that a reaction to the electromagnetic EMI radiation can occur only if it was actually measured.